Map design and layout
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- 6. Curves of various types
DRAWING EQUIPMENTS
Some of the equipments used in manual drawing of maps are as follows: 1. Drawing board or table 2. Drafting machine 3. T-square 4. Magnifying glass 5. Straight edge-12” scale and a slide rule 6. Curves of various types Maps are usually drawn on drawing tables manufactured specially for drafting purposes. A drawing table consists of a drawing board measuring at least 24” x 18” made of soft wood. A drawing table with a board is preferable. Drawing tables have mechanisms for adjusting the height as well as the tilt. The drawing paper should be affixed to the board either with a tape or thumb tacks. The latter leave holes and hence should be fixed only on the extreme corners. They also obstruct the movement of the T-square. Tapes are therefore preferable. A special kind of table called tracing or light table is a must in a cartographic laboratory. It is used in tracing on an opaque surface. It differs from an ordinary drawing table in that its surface is made of glass and not of soft wood. The glass is illuminated from beneath. A table can also be custom made which combines the functions of a drawing and a tracing table. In the board of the table on opening of, say, 12” x 9”, can be made to fix a glass. All tables and drafting machines must be properly lighted. Cartographic work puts lot of strain on the eyes. The lights should be such that they do not leave shadows and are adjustable. It is desirable to use fluorescent lamps. A T-square and a set of triangles are used in line drawing work. T-squares are made of metal or solid wood. One with transparent plastic edges is better, for it enables the draugftsman to see the drawings below. It slides up and down the side of the table or board. The triangles help in drawing vertical lines with varying slants. The curves of various types help in the drawing of curved lines. For smaller and sharp curves, a set of ‘French Curves’ is enough, bur for large curves one has to take recourse to railway curves or spine with weights. Recently flexible curves of different make have also been introduced for drawing curves of various shape and sizes. Fot example, Japanese flexible curve is made of rubber with small steel balls inside the rectangular tube with leveled edge. It is of different lengths which could be moulded and be given the required shape. Magnifying and reducing glasses are useful in judging the look of the drawings at various scales of reduction and enlargement. Stencils of symbols of various types, if at hand, can help in quick drawing of symbols. There are a number of drawing instruments one can get in a drawing box. It is better to have complete set, because the case in which the instruments are kept provides a convenient storage place. Download 191.32 Kb. Do'stlaringiz bilan baham: |
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